For example, Patent Literature 1 discloses a trench-gate vertical MOSFET including an epitaxial layer formed thereon with an active cell array and a gate bus area, a gate trench formed in the active cell array, a gate oxide film formed in the gate trench, a gate electrode made of polysilicon embedded in the gate trench, a trench formed in the gate bus area and being connected to the gate trench, and a gate bus including polysilicon embedded in the trench so that the surface of the epitaxial layer is covered in the gate bus area.